ROOM III. HUMERUS OF THE IGUAXODON. 287 



" Reports on British Fossil Reptiles," Professor Owen states 

 that this bone corresponds with certain bones of the foot 

 found at Horsham ; l but both extremities of the fossil in 

 question entirely differ from the articulating surfaces of all 

 the metacarpals and metatarsals of the Iguanodon that have 

 come under my observation ; a comparison with the humerus 

 from the Isle of Wight will at once establish its true 

 relations. 



This bone was obtained from the Wealden deposits on the 

 southern shore of the island, by Mr. Fowlstone, to whom 

 I am indebted for permission to have a cast taken of it : it is 

 figured in Lign. 60. It is perfect, with the exception 

 of the outer tuberosity of the head ; its dimensions are as 

 follow : 



Greatest length '3 feet. 



Length in a straight line from the inner tubercle of 



the head to the inner condyle 31 inches. 



From the outer tubercle of the head to the external 



condyle 33 



Circumference of the head 23^ 



round the condyles 21 



Circumference of the shaft at the deltoid crest . . 19 

 one-third from the dis- 

 tal extremity 16^ ,, 



The medullary cavity only extends to within one-third of the 

 top of the bone ; it is three inches in diameter : the greatest 

 thickness of the wall of the shaft is one inch. 



The head of the bone presents the usual posterior pro- 

 tuberance of the humerus in Lizards, but the epiphysis of this, 

 as well as of the distal extremity, is wanting, as is the ease 

 in all the long bones of the Wealden reptiles. At about three 

 inches from the top, the ridge or crest for the insertion of the 

 deltoid muscle is considerably developed, and extends fifteen 

 inches down the shaft, which rapidly contracts below, and 

 finally expands to form the condyloid extremity. The ar- 

 ticular face of the latter is divided into two nearly equal con- 

 dyles ; the inner or ulnar segment is traversed by an anterior 

 furrow, which is more strongly marked in the humerus of a 

 younger individual in my cabinet ; the posterior or olecranal 



1 " The bone of the Maidstone Iguanodon (marked 7 in the figure above 

 cited in the ' Wonders of Geology ') corresponds with the above described 

 bones of the foot" Professor Owen. "Brit. Assoc. Rep." p. 140. 



